This is a huge topic.
I think the first step to doing programmatic advertising on mobile the right way is to understand where programmatic has an advantage over 1) Facebook / Google and 2) SDK traffic from networks like eg. Unity.
For #1, programmatic advertising can be more efficient than Facebook or Google when you have already scaled Facebook and Google to a saturation point. In other words: for user acquisition, Facebook and Google will almost certainly be more performant for you on a profitable marginal dollar basis than buying programmatically from an exchange. Retargeting is a different story: you can absolutely outperform Facebook or Google with exchange traffic for retargeting. But in acquiring new users: if you can do it profitably on Facebook or Google, then you should. I genuinely believe that exchange buying should be incremental to Facebook and Google, not something that competes with those channels for budget.
Which brings us to #2: why would buying directly from an exchange be more efficient than buying from an ad network? One reason is that you're not operating in mobile gaming, since ad networks disproportionately service mobile games and network traffic tends to perform poorly for non-gaming apps. Another reason is that you have better, or more granular data than a network could have -- usually in the form of purchase history data for a large set of advertising IDs. If you have that, even for a mobile game, you can outperform ad networks.
If you don't have user-level data that you can attach to advertising IDs, then ad networks will outperform your own efforts on programmatic until you can get it. So how do you get it? You spend a lot of money acquiring it through running ROAS-centric campaigns programmatically and tracking bid levels for advertising IDs. This is expensive. You can't be efficient on programmatic by using the same buying tactics as with ad networks and trying to value cohorts on the basis of demographic features like geo and platform (eg. a US iPhone X user is worth $Y to us). With programmatic buying, to be efficient, you need to be attaching a value to a specific advertising ID, and it's very, very expensive to acquire data on a large number of advertising IDs via exchange buying.
So how do you get started? One way is to acquire lots of user behavioral data through your apps via other means (eg. buying on Facebook) and then leverage that with programmatic campaigns. Another way is to buy a company that has a huge user base. And a third way is to not directly manage your own programmatic campaigns but work with an agency that can operate on a sort of hybrid model and run cohort-focused programmatic campaigns with more features than you can, because they have aggregated a huge volume of campaign data.
That third option is how most companies dip their toes into programmatic.